1. Field of the Invention
The present invention relates to apparatus and methods for repairing ligament damage in a joint by providing a ligament graft member with proper position and fixation.
2. Description of Prior Art
In prior art, various methods of repairing damaged ligaments and joints, such as the anterior cruciate ligament (ACL) in a knee, have been advanced, including installing ligament graft members such as artificial ligaments. These ligament grafts may be portions of tendons that have been taken from other parts of the body. The ligament grafts are generally fixed in tunnels in or to the surfaces of the two bone parts or segments forming the joint by fixation screws, sutures, staples or other securing means. The problem has been that such ligaments will tend to loosen or rupture when exposed to joint motion during daily activities. The tunnel exit hole or port locations or other fixation points in the femur and on the tibia for such ligament graft members have been provided with the graft member then across between the interface of the two bone sections forming the joint. The graft members are anchored to the bone sections, and it has been known to preload such ligament grafts before they are fixed into position. However, it is desired that the length of and the loading on such ligament grafts does not change substantially during the range of motion of the joint and obtaining the desired positioning of the effective attachment site, and the length of such ligaments has been a drawback in any reconstructive surgery. Reproducibility of such reconstruction also remains an elusive goal.
Prior art efforts have concentrated on precisely locating the openings for the tunnels for such grafts and the attachment sites to overcome the problem of excessive shortening and lengthening experienced by the replacement ligament graft. Attempts to precisely locate such ligaments through the use of apparatus that locates the bone tunnels accurately has been explained and reviewed in U.S. Pat. No. 4,739,751. It is explained in that patent that some change occurs in the natural ACL as the knee joint flexes, but many surgeons seek an "isometric" relation of ligament grafts which means no change in attachment site distance as the tibia and femur flex.
A surgical drill guide for making tunnels for ligament grafts is also shown in U.S. Pat. No. 4,257,411. However, while proper location of the tunnels is a concern, it is generally believed that accurately and evenly loading segments or strands of reconstructive ligaments, whether artificial or natural and thus controlling the length, as well as accurately placing the attachment site leads to more reliable rehabilitation and repair of injured joints.